Subtraction within 100: Mental Strategies & Number Bonds

Free sample questions, a clear explanation, and 5 practice skills with an AI tutor that guides without giving the answer away.

Sample questions

1. What is 23 - 5?

○ 17

✓ 18

○ 28

○ 22

Answer: 18 — Think: 23 - 3 makes 20. How much more do you need to subtract from 20?

2. Find the answer: 31 - 4.

○ 35

○ 26

✓ 27

○ 37

Answer: 27 — Break 4 into 1 and 3. First subtract 1 from 31. Then subtract 3 from your new number.

3. What is 45 minus 8?

○ 43

○ 53

○ 36

✓ 37

Answer: 37 — Use number bonds! Break 8 into 5 and 3. Subtract 5 from 45 first.

Subtract a 1-digit number from a 1-digit or 2-digit number mentally using number bonds.
Subtract multiples of 10 from 2-digit numbers mentally.
Subtract two 2-digit numbers without regrouping using place value charts.
Subtract two 2-digit numbers with regrouping using concrete manipulatives (base-ten blocks).
Imagine you have $75 and spend $28. Describe two different mental strategies you could use to figure out how much money you have left.

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